Add Grafana dashboard for Prometheus datasource

Change-Id: Icacb0ca22a34f1ff438a895700040563d250bac9

linux/meta/grafana.yml

@@ -1,4 +1,9 @@
 dashboard:
-  linux:
+  linux_prometheus:
+    datasource: prometheus
+    format: json
+    template: linux/files/grafana_dashboards/system_prometheus.json
+  linux_influxdb:
+    datasource: influxdb
     format: json
     template: linux/files/grafana_dashboards/system_influxdb.json